Caption: Microsporidiosis life cycle. Diagram showing the life cycle of the spore-forming unicellular Microsporidia parasites that cause microsporidiosis. Microsporidia are only able to survive inside host cells. They produce resistant spores that are released into the environment, where they are able to survive for an extended period before infecting another host cell through a polar tube (seen in stages 2 and 3). Microsporidiosis is mainly found in individuals with a compromised immune system.